The present invention relates to the field of steganography and in particular to steganography using a digital image.
Digital images are becoming more and more commonplace, and nowhere are these images more prevalent than on the Internet""s World Wide Web. The vast majority of today""s World Wide Web pages are decorated with color images and, thus, people browsing through the Web no longer pay special attention to sites containing images or to the downloading of image data from the Web.
The abundance of digital images posted on the World Wide Web has led to the development of steganographic, or information hiding, programs aimed at invisibly marking copyrighted images to aid in enforcement of the copyright by the copyright owner. In recent years, several steganographic programs have been posted on the World Wide Web. Most of these programs use image data for the container, or carrier, of the confidential information and some use the least significant bits of the image data to hide the confidential informnation. Other programs embed the confidential information in a specific band of the spatial frequency component of the carrier, while still others make use of the sampling error in image digitization. However, each of these steganographic methods have a relatively small information hiding capacity, allowing only 5-15% of the carrier image to hide information. This capacity is generally sufficient for xe2x80x9cwater markingxe2x80x9d or placing a digital xe2x80x9csignaturexe2x80x9d onto computer data, but is generally insufficient for confidential human to human communications applications.
The explosion of the Internet has also increased concerns by network users over the security of Internet communications. For example, Internet e-mail is not a reliable means for sending confidential messages as these communications are easily intercepted. This ease of interception has led to the development and commercial distribution of many encryption programs. However, there are some cases when a user may wish to send a message to a person without the fact that a message has been sent being noticed by anyone else. Encrypting the message cannot solve this problem as encryption can hide the content of the message, but cannot hide the message data itself. Thus, anyone can intercept the xe2x80x9cunreadable messagexe2x80x9d and know that a message has been transmitted between the parties. Though appearing to be innocuous, this type of information may be very important to people such as unscrupulous business competitors or securities dealers, or even to organized crime figures, who may be keeping the sender or receiver under surveillance. Therefore, there is a need for a way to transmit data without the risk of another intercepting either the content of the message or the fact that a message has been sent.
Notwithstanding its usefulness in safeguarding human to human communications, high volume data embedding techniques also could be useful in a number of other areas. For example, certain personal data may be embedded within an image on a credit card, identification card, passport or the like in order to prevent counterfeiting or falsification. In addition, it is contemplated that sound data could be embedded within digital photographs to allow these sounds to be played when the image is viewed.
Therefore, a method of hiding a relatively large amount of confidential data in a digital image for downloading by another that eliminates the risk of a third party intercepting the content of the message and eliminates the risk of a third party becoming aware of the fact that a message has been sent, is not known in the art.
The present invention is a technique for hiding confidential information in a color image that is not based on a programming technique, but rather on a property of the human vision system. Because of its relation to human vision properties, the technique of the present invention provides an information hiding capacity of as much as 50% of the original image data and, in some circumstances, may provide hiding capacities in excess of 50%.
In its basic form, the method of the present invention includes the steps of transforming a dummy image from PBC to CGC system, segmenting each bit-plane of the dummy image into informative and noise-like regions by using a threshold value (xcex1), arranging the confidential file into a series of confidential blocks, conjugating blocks that are more complex than a threshold value, embedding each confidential block into the noise-like regions of the bit-planes, recording conjugated blocks in a xe2x80x9cconjugation mapxe2x80x9d, embedding the conjugation map within the image, and converting the embedded dummy image from CGC to PBC.
In another embodiment, the method includes the steps of dividing the image into regions, determining an xe2x80x9cembedding depthxe2x80x9d in each region based on a complexity measure, arranging the confidential file into a series of confidential blocks, embedding the confidential blocks in the least significant bit planes of each region according to the computed embedding depth, recording the embedding depths in a xe2x80x9cdepth mapxe2x80x9d, and embedding the depth map within the image
Therefore it is an aspect of the invention to provide a steganography method that results in a large information hiding capacity.
It is a further aspect of the invention to provide a steganography method that prevents third parties from reading a confidential message.
It is a further aspect of the invention to provide a steganography method that prevents third parties from knowing that a confidential message has been sent.
These aspects of the invention are not meant to be exclusive and other features, aspects, and advantages of the present invention will be readily apparent to those of ordinary skill in the art when read in conjunction with the following description, appended claims and accompanying drawings.